1. Field of the Invention
The present invention relates to a fix replenisher control system for use in processors of photosensitive material.
2. Description of the Prior Art Automatic photographic film and paper processors transport sheets or webs of photographic film or paper through a sequence of processor tanks in which the photosensitive material is developed, fixed, and washed, and then transports the material through a dryer. It is well known that photographic processors require replenishment of the processing fluids to compensate for changes in the chemical activity of the fluids.
First, it has been recognized that replenishment is necessary to replace constituents used as photosensitive film or paper is developed in the processor. This replenishment is "use related" or "exhaustion" chemical replenishment. Both developer and fix solutions require exhaustion replenishment.
Second, chemical activity of the developer solution due to aerial oxidation occurs with the passage of time regardless of whether film or paper is being processed. Some replenishment systems provide additional replenishment of an "anti-oxidation" (A-O) replenishment solution which counteracts this deterioration.
Replenishment systems were originally manually operated. The operator would visually inspect the processed film or paper and manually operate a replenisher system as he deemed necessary. The accuracy of the manual replenisher systems was obviously dependent upon the skill and experience of the operator.
Various automatic replenishment systems have been developed for providing use-related replenishment. Examples of these automatic replenishment systems include U.S. Pat. Nos. 3,472,143 by Hixon et al; 3,529,529 by Schumacher; 3,554,109 by Street et al; 3,559,555 by Street; 3,561,344 by Frutiger et al; 3,696,728 by Hope; 3,752,052 by Hope et al; 3,787,689 by Fidelman; 3,927,417 by Kinoshita et al; 3,990,088 by Takita; 4,057, 818 by Gaskell et al; 4,104,670 by Charnley et al; 4,119,952 by Takahashi et al; 4,128,325 by Melander et al; and 4,134,663 by Laar et al. Examples of prior art replenisher controls for providing both exhaustion and anti-oxidation replenishment are shown in U.S. Pat. Nos. 3,822,723 by Crowell et al and 4,174,169 by Melander et al.
In the past, fix replenishment has been an inaccurate and costly proposition. Typically fix replenishment has been provided in a fixed ratio to developer exhaustion replenishment. This proves to be very inefficient as far as fix replenishment is concerned because the more developer which is used or exhausted, the less fix which is used or exhausted. The only point at which correct volumes of replenishment for both fix and developer exhaustion are reasonably accurate with prior art systems is at 50% density of the photosensitive material. The direct coupling of developer and fix replenishment, as in the past, results in underreplenishing of fix when low density materials are processed, and overreplenishing of fix when high density material is processed.